Anastigmatic objective.



O. GRAF.

ANASTIGMATIG OBJECTIVE.

APPLICATION FILED D110. 24, 1909.

Patented Jan. 10, 1911.

ATTORNEYS "UNITED STAlllfQiiltri Specification of Letters Ilhziteut,

cnmsrornnn GRAB, or new firemen.

nn vromns, or wnsntnrerruu', :r.

Preterm. Jun, Mi, Itililt'it.

and State of New York, have inren l u new and Improved ihllflfilllglilfiilfi @b'jtlciiiirfi, r

of whiohthe following is s ffuli, enact (lescriptionr This invention relates s eoinpourn'l lens to he use'cllin photographic instruur its er. the like, em. consists of e plurality oi? spncerl lenses of substantially the saline reiiuctire incic'ir em having curvatures oi? such e churae ter that the inner lenses are symrnetricul with respect'to each other, er

l..ir, unri the inner lenses unsymmetrieui with respect to eueh other, thereby forrnii'rg a comporuui lens, Whiel'i, as a whole, is unsymmetrical.

This invention ernhociies not only new construction but u new principle oil? constrrm tioh, in that the three chief uherrutionse the spherical aberration, nerne uni the ustignmtism nre expressed as fuinr "one oi? the eightraclii of curvature, thus mu iug an erect algebraic solutien for the ran. .1 necr sery to hring'these aberrations to new. iitueh "e sohrtion would not be possible withnut first securing flatness of field by using glass all of the same index and gaining nearly nil. the

foeul. pewer by sepurution.

An object of this invention is to provide an optical piece which. nun he easily n'mnufnctu'liecl and easily emrecteti, and. which 5 will have none of the defects, such. as spine-i earl and chronmtic :ihermtion, astig g'nmtism, convexity of-the inuige, coins, distortion or the like, and which will also tulre e picture with great sharpness and detail. This unit 40 further objeets, together with the emisti'um .tion and combination of parts, will. he more fully rloscriherl hercimriter nnol 1nu'ticuhrrl' sot forth in the claims.

Reference is to be had, to the ETICCO-IUDRHIY- ing drawings forming a, part 0i this specie ficntion, in which the figure repr outs diagrammatic illustration of the lenses corn-- posingthis optical piece and their reiutire positions, magnitudes, curvatures enrl thieieoonesses.

The line of sight passes from left tr as indicated by the mrrow in the The optical piece is preferably compose fourlenses 1, 2, 3 and. at, spaced apart :trern each other so as to form positive nieniscuses.

The rurl'i nnrl thicknesses of the various distances spurt ere particuhe, in "hicle shove tuhle that the stone hes so Hunter 21 k iii '3 i intr est to tr 1 i. are or meters of lei l. unrl. I l,

.ricul urui 19 h inspect to ruch o .M,

" li-etier nor the none cf .3] his s 'ynrn e lens can 11; oi very high. quality. 3 are r 'n'muui cul other, 'ep i; The lenses 2 with respectto each rnijil y rr" ,utivc or die in these two "cal in curve liit't'ilhunt in oru iesite- 1s it ere intent tained almost entirely by separating the ,component lenses, that is, if the component lenses were shoved together the combina- {tion would have a focal length so great as to be useless. For example, in my lens of equivalent focal length 160, the focal lengths of the components are respectively +62, -75, 'Z5 and +75. The separations are S, 2.4 and 8. If the lenses were shoved together the equivalent focal length would be The purpose of these first two principles .of construction is to secure a flatimage field without restricting the curvatures of the lens surfaces, leaving these free to take care of the five remaining aberrations.

There is thus formed an optical piece with the first and last lenses positive and unsymmetrical, and the second and third lenses negative andv symmetrical, and all the four component lenses of which are made of glass of the same index of refraction, 1.6253, and in which the three chief aberrations-sphcrical aberration, coma and astigmatism, are

functions of the eight radii of curvature.

ing symmetrical and symmetrically an ranged between the positive lenses, and the positive lenses being oi; different tlncknesscs and having different radii of curvature and spaced from the negative lenses :1 distance greater than the negative lenses are spaced.

apart, said positive lenses being arranged with the faces having the shorter radii of curvature on the outer side, and all of the said lenses having the same index of refraction for the principal color.

2.-An anastigmatic objective comprising four lenses with adjacent lenses air spaced from each other and including two positive and two negative lenses with the negative lenses adjacent each other and the positive lenses on the outer side of the two negative lenses, said lenses having the same index of refraction for the principal color, one of the positive lenses having faces whose radii of curvature are approximately 46.2 and 24:1.6 and the other positive lenses having faces whose radii of curvature are approximately 417.5 and 52.70 and the'radii of curvature of the negative lenses being approximately 92.25 and 95.4, all substantially as set forth.

3. An anastigmatic objective, comprising a positive lens having faces Whose radii of curvature are 16.2 and 2e15, a negativelens spaced apart from said positive lens by an air space and having faces whose radii of curvature are 92.25 and 95A, a negative lens spaced apart from said first-mentioned negalive lens by an air space' and .havinn faces whose radii of curvature are 95.4 and 92.25, and a. positive lensspaced apart from said last-mentioned negative lens in an air space and having faises whose ra. iijof curvature are 417.5 and 52.70, all of said lenses having the same refrnctiveindex. in testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses. CHRISTOPHER GltAF.

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